It is known from "Die Nahrung", Volume 4, 1960, No. 4, pages 310-323, in particular page 322, Abstract or Summary, that nicotine N'-oxide contained in smoking tobacco forms nicotine on smoking and leads to an increase in the nicotine content of the mainstream smoke and slipstream smoke.
The invention is based on the discovery that the cis-isomer of nicotine N'-oxide causes a considerable deterioration in the taste of the smoke. Accordingly, the invention relates to a smoking product, the smoke of which has an increased nicotine content due to the addition of nicotine N'-oxide, wherein the above-mentioned impairment of the taste of the smoke by the cis-isomer is avoided.
The term "smoking product", used here, is to be understood as cut tobacco, pipe tobacco, cigarettes, cigarillos or cigars of tobacco with or without added non-tobacco materials and/or reconstituted tobacco. The smoking product of the invention can have been produced with or without a wrapper material, the possible wrapper materials used being cigarette paper, cigar wrappers or cigarillo wrappers of tobacco or non-tobacco materials.
Mixtures of isomers of nicotine N'-oxide were obtained for the first time by oxidation of nicotine with aqueous hydrogen peroxide, cf. Chem. Ber. 24, 61-67 (1891). An improvement of this process, using a nicotine/hydrogen peroxide molar ratio of 1:3, is described in J. Org. Chem. 24, 275-277 (1970). A particular disadvantage of this process is the long reaction period of 2-3 days and the large excess of oxidizing agents, which prohibits economical exploitation of this process. In addition, it was not possible to isolate the resulting mixture of isomers of nicotine N'-oxide; it was necessary to isolate and characterize the end products as the picrates.
Substantially shorter oxidation periods can be obtained in the preparation of the mixture of isomers of nicotine N'-oxide when the oxidation is carried out with organic peracids in accordance with J. Org. Chem. 35, 1721-1722 (1970). However, the desired reaction products require more elaborate purification work; in addition, such a process for the preparation of nicotine N'-oxides is uneconomical because of the high price of organic peracids.